Two stage hydraulic cylinder



Aug. 30, 1966 R. s. WAITE TWO STAGE HYDRAULIC CYLINDER 2 Sheets-Sheet 1 Filed July 21, 1964 M w m h w R INVENTOA.

BY M Attorney:

Aug. 30, 1966 R. s. WAITE TWO STAGE HYDRAULIC CYLINDER 2 Sheets-Sheet 2 Filed July 21, 1964 m 6 m m ww vm mm mm wwmv an mm m m mm t N E A mm mm H w W 1 v ill ll .III. I 5? i g 0 m We E d W I I I r MN MW \q %m G 1 h vw mm vm um Ev wm m wm h D w mm mm wv s 9v j mm mm m I 9v United States Patent 3,269,275 TWO STAGE HYDRAULIC CYLWDER Richard S. Waite, Columbus, Nebr., assignor to The Soil Mover Company, Inc., a corporation of Nebraska Filed July 21, 1964, Ser. No. 384,084 6 Claims. (Cl. 92-52) This invention relates to a novel and useful two stage fluid motor of the extendible type and which is adapted to be actuated 'by air or hydraulic fluid.

Most fluid motors of the extendible type exert a steady force at a constant speed when operatively connected to a source of fluid under constant pressure. There are various types of two stage fluid motors of the extendible type but these two stage cylinders or fluid motors have in the past proved not too successful because of their telescoping cylindrical sections which present sealing problems, especially when the fluid motors are to be utilized in dusty atmospheres.

Accordingly, the multistage fluid motors or cylinders of the type including a plurality of telescoped sections are at best a maintenance problem in addition to being costly to manufacture. Accordingly, conventional types of multistage fluid motors or cylinders are not utilized in environments which would subject the sliding portions of the telescope-d sections to dirt and the like.

In the earth moving art many types of road graders are provided with horizontal scoops which are open at their forward ends and are adapted to be advanced along the ground which is to be removed. As the earth mover advances forwardly, earth is forced into the scoop toward the rear thereof. Then, when it is desired to eject a load of dirt from the scoop, an ejecting gate or panel disposed in the rear of the scoop is moved forwardly so as to eject the dirt from the scoop. Many earth movers of this type utilize a cable system for forwardly displacing the dirt ejecting gate but these cable systems are very easily overstressed and therefore subject to breakdown. Other similar types of earth movers utilize hydraulic cylinders for moving the dirt ejecting gate forwardly in the scoop body but these hydraulic cylinders must be capable of exerting tremendous initial forces in order to slide the entire load of dirt forwardly in the scoop. While this tremendous initial thrust can be made available with large diameter hydraulic cylinders, after one-half of the load of dirt has been ejected, the full thrust available by the hydraulic cylinders is not required and a faster acting less powerful hydraulic cylinder could be utilized to eject the last portion of the load of dirt.

It is in this environment that the two stage fluid motor of the instant invention is particularly well adapted to be utilized. While conventional two stage fluid motors of a type hereinbefore set forth could also be utilized, inasmuch as earth moving equipment must be capable of operating efliciently in dusty atmospheres, conventional forms of multisection telescopic hydraulic cylinders have not proven successful.

The two stage fluid motor of the instant invention includes only one sliding surface which could be exposed to the atmosphere and therefore susceptible to dust falling thereon. However, this one sliding surface may be kept clean by suitable protective boots and/ or seals and therefore the two stage cylinder of the instant invention is particularly well adapted to function as the motive force for effecting reciprocation of the ejector gate of a road scraper.

The main object of this invention is to provide an improved two stage fluid motor constructed in a manner enabling it to apply a two stage thrust on a road grader ejector gate and particularly well adapting it to be utilized in dusty atmospheres without the dusty atmosphere having adverse effects thereon.

Another object of this invention is to provide a two stage fluid motor or hydraulic cylinder in accordance with the immediately preceding object and constructed in a manner whereby it may be readily installed as a replacement for existing types of multisection telescopic fluid motors.

A final object of this invention to be specifically enumerated herein is to provide a two stage fluid motor in accordance with the preceding objects which will conform to conventional forms of manufacture, be of simple construction and dependent in operation so as to provide a device that will be economically feasible, long lasting and relatively trouble free.

These together with other objects and advantages which will become subsequently apparent reside in the details of construction and operation as more fully hereinafter described and claimed, reference being had to the accompanying drawings forming a part hereof, wherein like numerals refer to like parts throughout, and in which:

FIGURE 1 is a fragmentary top plan View of the rear portion of a conventional form of road grader shown with the two stage hydraulic cylinder or fluid motor of the instant invention operatively connected between the frame of the road grader and the ejector gate thereof for oscillating the ejector gate between forward dump positions and rearward retracted positions;

FIGURE 2 is a side elevational view of the embodiment illustrated in FIGURE 1;

FIGURES 35 are longitudinal sectional views of the two stage fluid motor of the instant invention taken substantially upon a plane passing along the longitudinal centerline of the fluid motor and showing the latter in different stages of operation; and

FIGURE 6 is an enlarged transverse sectional view taken substantially upon the plane indicated by the section line 6-6 of FIGURE 3.

Referring now more specifically to the drawings, the numeral 10 generally designates a conventional form of road grader including a main frame 12 having rear wheels 14 and a bucket or scoop 16 with a cutting blade 18 secured to its forwardmost lower lip. As the scoop 0r bucket 16 is lowered into engagement with the ground 20, dirt will be forced up into the scoop 16 upon forward movement of the grader 10 and rearwardly of the scoop 16 into engagement with the ejector gate 22.

The ejector gate 22 may be supported from the scoop '16 in any convenient manner for oscillation between the rearmos-t retracted position illustrated in FIGURES 1 and 2 of the drawings and a forwardmost position disposed immediately rearwardly of the cutting blade 18. The two stage fluid motor of the instant invention is generally referred to by the reference numeral 24 and is shown supported from the main frame .12 with the free end of its piston rod .25 secured to the ejector gate 22. Thus, upon extension of the fluid motor 24, the ejector gate 22 will be shifted toward the forward end of the scoop 16 in order to eject any dirt which has accumulated therein.

With attention now directed more specifically to FIG- URES 3-6 of the drawings, it may be seen that the fluid motor 24 includes an outer cylinder 26 closed at one end by means of a fixed end wall 28 and at the other end by means of a removable closure wall 30. The closure wall 30 has a bore 32 formed therethrough and the rear end of the piston rod 25 is slidably received through the bore 32.

The closure wall 30 includes seal means 34 and 36 for ensuring a fluid tight seal between the closure wall 30 and the cylinder 26 as well as the piston rod 25.

An inner cylinder 88 is disposed in the outer cylinder 26 and includes a diametrically enlarged piston head por tion 40 on one end. The inner cylinder 38 includes an integral end wall 42 having a shank portion 44 formed integrally therewith whose free end is externally threaded as at 46. The piston head portion 40 includes suitable sealing rings 48 and 50 and is secured on the shank portion 44 by means of a suitable fastener 52.

The end of the 'inner cylinder 38 remote from the piston head portion 40 has a closure wall 54 removably secured therein and the closure wall 5-4 has a bore 56 formed therethrough which is in axial registry with the bore 32. A piston head portion 58 is secured to the end of the piston rod 25 disposed within the inner cylinder 68 by means of a suitable fastener 60 and it may be seen that the piston head portion 58 also includes seal means 62 and 64 corresponding to the sealing rings or seal means 48 and 50.

The closure end wall 30 also includes a dust seal 65 for wiping dust from the piston rod 25 as it is advanced rearwardly into the outer cylinder 26.

The opposite ends of the outer cylinder 26 each have a fluid inlet and outlet opening 66 formed therein which is adapted to be communicated with a suitable source of fluid under pressure. Further, it may be seen that the forward end of the inner cylinder 38 also includes a fluid inlet and outlet opening 68 and that the shank portion 44 has an inlet and outlet bore 70 formed therethrough.

In operation, and assuming that the fluid motor 24 is in its retracted position illustrated in FIGURE 5 of the drawings, fluid under pressure is admitted into the outer cylinder 26 by means of rear inlet and outlet opening 66. The piston head portion 40, being of greater diameter than the piston head portion 58, is then urged forwardly until such time as the closure wall 54 abuts against the closure wall 30. At this point, approximatley one-half of the load of dirt within the road grader or scraper has been ejected and the fluid admitted into the outer cylinder 26 passes through the bore 70 and into the inner cylinder 38 and thereby urges the piston head portion 58 from the position illustrated in FIGURE 4 of the drawings to the position illustrated in FIGURE 3 of the drawings. It is of course to be understood that a given amount of linear displacement of the piston head portion 40 requires the introduction of a greater amount of fluid into the outer cylinder 26 than that quantity of fluid introduced into the inner cylinder 38 operative to effect the same amount of linear displacement of the piston head portion 58. Accordingly, after the initial portion of the load of dirt within the scoop 16 has been ejected, the remaining portion of the load of dirt is ejected by displacement of the piston head portion 58 relative to the inner cylinder 38, which displacement, assuming the same rate of supply of fluid under pressure to the interior of the inner cylinder 38, is more rapid than the previous displacement of the piston head portion 40.

Accordingly, the tremendous initial thrust for initially ejecting dirt from the scoop 16 is provided by means of the larger piston head portion 40 and the more rapid and less forceful thrust for ejecting the remaining portion of the load of dirt from the scoop 16 is effected by displacement of the piston head portion 58.

It is to be noted that only the external surfaces of the piston rod 25 disposed exteriorly of the outer cylinder 26 are exposed to dust. It is only this one surface that must be maintained clear of dust beforev it enters the outer and inner cylinders 26 and 38. However, the dust seal 65 may be of any suitable type operable to this end.

Finally, the fluid motor 24 need not be limited to twostage operation. It may be constructed so as to afford additional stages of operation merely by the addition of further inner cylinders of diflerent diameters. Still further, the elfective length of each stage of operation may be readily varied by changing the etfective length of the corresponding inner cylinder.

The foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly all suitable modifications and equivalents may be resorted to, falling within the scope of the invention as claimed.

What is claimed as new is as follows:

1. A two-stage fluid motor of the extendible type ineluding an outer cylinder closed at one end and including a closure wall at the other end having a bore formed therethrough, an inner cylinder reciprocal in said outer cylinder and closed at a first end thereof corresponding to one end of said outer cylinder, said first end defining a diametrically enlarged first piston for said outer cylinder, said inner cylinder including a closure wall at its second end having a bore formed therethrough axially aligned with the first-mentioned bore, a piston rod physically extending through and reciprocal in said bores in fluidtight sealing engagement with said closure walls and including a second diametrically enlarged piston on the end thereof disposed in said inner cylinder, each of the opposite end portions of said outer cylinder including free flow fluid passage means defining first fluid inlet and outlet passage means for free passage of fluid under pressure into and out of said opposite end portions of said outer cylinder and opening into said outer cylinder at one pair of corresponding ends on the corresponding side of said first piston when the latter is disposed in its corresponding limit position of reciprocation and outwardly of said outer cylinder at the other pair of corresponding ends thereof, said inner cylinder including free flow fluid passage means defining second fiuid inlet and outlet means opening into said inner cylinder at a point spaced beyond the limit of movement of said second piston therein toward the fully extended position at one end and directly into the area of said outer cylinder forwardly of said first piston in the direction of its movement toward the extended position at its other end and for free passage of fluid under pressure between said point and said area, and free flow fluid passage means formed through said first piston communicating said one end of said outer cylinder and the corresponding end of the interior of said inner cylinder defining third fluid inlet and outlet passage means for free passage of fluid therethrough in both directions.

2. The combination of claim 1 wherein said inner cylinder has a length approximately one-half the effective length of the interior of said outer cylinder.

3. The combination of claim 1 wherein said closure walls are removably secured in the corresponding ends of said inner and outer cylinders.

4. The combination of claim 1 wherein said third fluid inlet and outlet passage means comprises a bore extending through said closed end of said inner cylinder.

5. The combination of claim 4 wherein said piston means on said piston rod is registrable with the inner end of the last-mentioned bore for closing the same when said piston rod is fully retracted in said inner cylinder.

6. The combination of claim 1 wherein said second fluid inlet and outlet passage means comprises a generally radial opening formed through said inner cylinder adjacent its closure wall.

References Cited by the Examiner UNITED STATES PATENTS 1,520,842 12/1924 Newman 9l169 1,855,266 4/1932 Van Eps 91-169 2,558,810 7/1951 Bent 91-169 2,965,988 12/1960 Monk 37176 3,138,884 6/1964 Hein 37-129 MARTIN P. SCHWADRON, Primary Examiner.

SAMUEL LEVINE, Examiner.

" Br T, CQBRIN, Assistant Examiner. 

1. A TWO-STAGE FLUID MOTOR OF THE EXTENDIBLE TYPE INCLUDING AN OUTER CYLINDER CLOSED AT ONE END AND INCLUDING A CLOSURE WALL AT THE OTHER END HAVING A BORE FORMED THERETHROUGH, AN INNER CYLINDER RECIPROCAL IN SAID OUTER CYLINDER AND CLOSED AT A FIRST END THEREOF CORRESPONDING TO ONE END OF SAID OUTER CYLINDER, SAID FIRST END DEFINING A DIAMETRICALLY ENLARGED FIRST PISTON FOR SAID OUTER CYLINDER, SAID INNER CYLINDER INCLUDING A CLOSURE WALL AT ITS SECOND END HAVING A BORE FORMED THERETHROUGH AXIALLY ALIGNED WITH THE FIRST-MENTIONED BORE, A PISTON ROD PHYSICALLY EXTENDING THROUGH AND RECIPROCAL IN SAID BORES IN FLUIDTIGHT SEALING ENGAGEMENT WITH SAID CLOSURE WALLS AND IN CLUDING A SECOND DIAMETRICALLY ENLARGE PISTON ON THE END THEREOF DISPOSED IN SAID INNER CYLINDER, EACH OF THE OPPOSITE END PORTIONS OF SAID OUTER CYLINDER INCLUDING FREE FLOW FLUID PASSAGE MEANS DEFINING FIRST FLUID INLET AND OUTLET PASSAGE MEANS FOR FREE PASSAGE OF FLUID UNDER PRESSURE INTO AND OUT OF SAID OPPOSITE END PORTIONS OF SAID OUTER CYLINDER AND OPENING INTO SAID OUTER CYLINDER AT ONE PAIR OF CORRESPONSING ENDS ON THE CORRESPONDING SIDE OF SAID 